Let all who believe that our fathers understood this question just as well as, and even better than, we do now, speak as they spoke and act as they acted upon it.  This is all Republicans ask—­all Republicans desire—­in relation to slavery.  As those fathers marked it, so let it be again marked, as an evil not to be extended, but to be tolerated and protected only because, and so far as, its actual presence among us makes that toleration and protection a necessity.  Let all the guarantees those fathers gave it be not grudgingly but fully and fairly maintained.

His counsel to the young Republican party was timely and full of wisdom.

A few words now to Republicans:  It is exceedingly desirable that all parts of this great Confederacy shall be at peace, and in harmony one with another.  Let us Republicans do our part to have it so.  Even though much provoked, let us do nothing through passion and ill-temper.  Even though the Southern people will not so much as listen to us, let us calmly consider their demands, and yield to them, if in our deliberate view of our duty we possibly can.

The address closed with the following impressive words: 

Wrong as we think slavery is, we can yet afford to let it alone where it is, because that much is due to the necessity arising from its actual presence in the nation; but can we, while our votes will prevent it, allow it to spread into the National Territories, and to overrun us here in these free States?  If our sense of duty forbids this, then let us stand by our duty, fearlessly and effectively.  Let us be diverted by none of those sophistical contrivances wherewith we are so industriously plied and belabored—­contrivances such as groping for some middle ground between the right and the wrong, vain as the search for a man who should be neither a living man nor a dead man,—­such as a policy of ‘don’t care’ on a question about which all true men do care,—­such as Union appeals, beseeching true Union men to yield to Disunionists, reversing the divine rule, and calling not the sinners but the righteous to repentance,—­such as invocations of Washington, imploring men to unsay what Washington said and undo what Washington did.  Neither let us be slandered from our duty by false accusations against us, nor frightened from it by menaces of destruction to the Government nor of dungeons to ourselves.  Let us have faith that right makes might; and in that faith, let us to the end dare to do our duty as we understand it.

The Cooper Institute speech made a profound impression upon the public.  All who saw and heard Lincoln on that occasion felt the influence of his strange but powerful personality; and acute minds recognized in the unsophisticated Western lawyer a new force in American politics.  This speech made Lincoln known throughout the country, and undoubtedly did more than anything else to secure him the nomination